I have been plagued by this this week. Its not pretty. My work flow is HDV captured as prores for all footage I shoot. This is a major BUG! I started to edit after capture and everything was fine. Closed FCP and when I relaunched all the clips in the viewer are now white and the sequence was offline. Even after I added the .mov to all the clips in capture scratch I couldn’t reconnect the media. I ended up re importing the clips after adding the .mov to all the clips and reediting the project. Major pain and time waster. I hope this gets fixed ASAP.
For now don’t edit anything until you change the extensions.
https://www.mediaartproductions.com